Energy and exergy analysis of using turbulator in a parabolic trough solar collector filled with mesoporous silica modified with copper nanoparticles hybrid nanofluid

Designing the most efficient parabolic trough solar collector (PTSC) is still a demanding and challenging research area in solar energy systems. Two effective recommended methods for this purpose that increase the thermal characteristics of PTSCs are adding turbulators and nanofluids. To study the effects of the two approaches on the energy efficiency of PTSCs, a stainless steel turbulator was used and solid nanoparticles of Cu/SBA-15 were added to the water with the volume concentrations of 0.019% to 0.075%. The generated turbulence in the fluid flow was modeled by the SST k–ω turbulent model. The results in daylight demonstrated that energy efficiency increases steadily by 11:30 a.m., and then, starts to drop gradually due to more irradiations at noon. It was observed that applying the turbulator to the studied PTSC has a significant influence on the enhancement of energy efficiency. Adding the nanoparticles augmented the average Nusselt number inside the solar collector in various studied Reynolds numbers. It was also found that the increase in volume concentrations of nanoparticles enhances heat transfer regularly

Evaluation of a Desktop 3D Printed Rigid Refractive-Indexed-Matched Flow Phantom for PIV Measurements on Cerebral Aneurysms

Purpose Fabrication of a suitable flow model or phantom is critical to the study of biomedical fluid dynamics using optical flow visualization and measurement methods. The main difficulties arise from the optical properties of the model material, accuracy of the geometry and ease of fabrication. Methods Conventionally an investment casting method has been used, but recently advancements in additive manufacturing techniques such as 3D printing have allowed the flow model to be printed directly with minimal post-processing steps. This study presents results of an investigation into the feasibility of fabrication of such models suitable for particle image velocimetry (PIV) using a common 3D printing Stereolithography process and photopolymer resin. Results An idealised geometry of a cerebral aneurysm was printed to demonstrate its applicability for PIV experimentation. The material was shown to have a refractive index of 1.51, which can be refractive matched with a mixture of de-ionised water with ammonium thiocyanate (NH4SCN). The images were of a quality that after applying common PIV pre-processing techniques and a PIV cross-correlation algorithm, the results produced were consistent within the aneurysm when compared to previous studies. Conclusions This study presents an alternative low-cost option for 3D printing of a flow phantom suitable for flow visualization simulations. The use of 3D printed flow phantoms reduces the complexity, time and effort required compared to conventional investment casting methods by removing the necessity of a multi-part process required with investment casting techniques

Application of stereoscopic PIV for hemodynamic studies of life-sized carotid artery models under pulsatile flow condition

One of the major causes of ischemic stroke is embolism of thrombi (i.e. blood clots) that are formed at the site of the atherosclerotic plaque in the carotid artery bifurcation. Certain hemodynamic factors, such as flow disturbances, shear stress forces, and recirculation are linked to thrombosis by enhancing and facilitating platelet activation and aggregation [1, 2]. Any alterations of the local flow patterns that can, in turn, induce altered hemodynamic factors can impact the level of thrombotic activity. Previous clinical studies have shown the association of certain geometrical features of the plaque, namely severity of stenosis (i.e. narrowing), plaque eccentricity (symmetry), and plaque ulceration (irregular surface) to the frequency of cerebrovascular events [3, 4]. As a gold-standard experimental technique, particle image velocimetry (PIV) can provide detailed analysis of spatially and temporally evolving flows. This technique has extensively been applied to hemodynamic studies, primarily to investigate the potential of thrombosis in mechanical heart valves (ref). To date, only three PIV studies (excluding echo PIV studies) have been reported in carotid artery models; Bale-Glickman et al. [5] applied planar PIV to two patientspecific stenosed carotid artery models, Vetel et al. [6] studied flow in a patient-specific model of a healthy carotid artery using stereo PIV, and Buchmann et al. [7] studied a healthy carotid artery model and compared results using tomographic and stereoscopic PIV. All studies were conducted assuming steady inlet flow; although they provide a baseline understanding of flow patterns, pulsatile flow conditions strongly impact the flow dynamics, introducing flow instabilities and high temporal gradients. We have developed a flow-measurement system applying stereoscopic PIV in a family of life-sized carotid artery models, representing a range of disease progression, under physiologically realistic flow conditions in order to characterize stenosed flow features and investigate the impact of the geometrical features of the plaque on downstream flow patterns. A detailed description of the experimental design features and challenges are described, along with sample results. To demonstrate the capability of this system, flow features extracted from a 70% concentrically stenosed model are presented

Highly polymorphic novel simple sequence repeat markers from class i repeats in walnut (Juglans regia L.)

Walnut (Juglans regia L.) is the most important species in the genus Juglans due to the high commercial value of its nuts and timber. Simple sequence repeats (SSRs) are considered as the markers of choice owing to their codominant nature. Since very few SSRs have been developed in walnut, this study aimed to develop numerous polymorphic SSRs from Class I repeats by using DNA sequences of the Chandler cultivar. In all, 800 SSRs were designed and tested in 8 Turkish, 3 French, and 5 US walnut cultivars, of which 88 (11%) did not produce bands, 161 (20.1%) were monomorphic, and 551 (68.9%) were polymorphic. In all, 2696 alleles were produced by the 551 polymorphic SSR loci in the 16 walnut cultivars, ranging from 2 to 14 alleles per locus with an average number of 4.9. Polymorphism information content ranged from 0.21 to 0.89 with an average of 0.62. Cluster analysis produced a very robust dendrogram. The walnut cultivars were separated into two main groups: All Turkish cultivars were included in one group, whereas the US and French cultivars were included in the other group. A set of 20 SSRs was selected for their high genetic diversity values to be used in further genetic studies in walnut. The novel SSR markers developed in this study could be used in future studies for constructing a genetic linkage map, analyzing population genetics, identifying parents, and conducting marker-assisted breeding, fingerprinting, and germplasm characterization in walnut. © TÜBİTAK.Firat University Scientific Research Projects Management Unit Türkiye Bilimsel ve Teknolojik Araştirma Kurumu: 214O140This project was financially supported by the Scientific and Technological Research Council of Turkey (Project No. TÜBİTAK TOVAG 214O140) and the Çukurova University Scientific Research Projects Unit (Project No. FYL-2015-4852)

Secure Consensus Averaging in Sensor Networks Using Random Offsets

Abstract — In this work, we have examined the distributed consensus averaging problem from a novel point of view considering the need for privacy and anonymity. We have proposed a method for incorporating security into the scalable average consensus mechanisms proposed in the literature. Random Offsets Method (ROM) is lightweight, transparent and flexible since it is not based on cryptography, does not require any change in the fusion system and can be used optionally by some nodes who care about their privacy. In this method, which is based on noisification of nodes ’ information, we achieve robustness against n − 1 colluding adversaries in a network of n nodes, which is maximum level of robustness against collusions. Convergence and collusion robustness of ROM are analyzed mathematically and through simulation. I